On further reading we could enable SCTP by default, as it shipped in R16B03 and is self-contained.

The other two are very much for testing, changing significant runtime behaviour:

```
--enable-dirty-schedulers - Enable the experimental dirty schedulers functionality. Note
that the dirty schedulers functionality is experimental, and not supported. This functionality
will be subject to backward incompatible changes. Note that you should not enable the dirty
scheduler functionality on production systems. It is only provided for testing.
```
and enable-native-libs compiles some stuff to binary instead of beam code. Various reports of applications that fail in weird places crop up from time to time. Hence as an option.

However both are of great interest to erlang developers atm.

I'll tweak the options to match the above, & re-push.